1. Field of the Invention
The present invention generally relates to a wireless communication system, a wireless communication terminal and a wireless communication method.
Priority is claimed on Japanese Patent Application No. 2005-128118, filed Apr. 26, 2005, the contents of which are incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
A typical wireless communication system may be a MIMO (Multi Input Multi Output) system that is designed to improve a rate of communication between a mobile station and a base station. In the MIMO system, each of the mobile station and the base station has a plurality of antenna elements for transmitting and receiving radio waves so as to establish a plurality of communication paths or propagation paths between the mobile station and the base station. A first one of the mobile station and the base station may transmit one or more signals or one or more sets of data to a second one thereof. In this case, the first one serves as a transmitter station and the second one serves as a receiver station. For example, the plural antenna elements of the base station transmit plural sets of data, respectively. The plural sets of data are different and separate from each other. The different and separate sets of data are mixed with each other on the propagation paths. The plural antenna elements receive the mixed sets of data and separate the mixed sets into the original plural sets of data that are separate and different from each other. This conventional technique is disclosed in Japanese Unexamined Patent Application, First Publication, No. 2002-44051. In the MIMO system, each of a transmitter station and a receiver station has a plurality of antenna elements. Other typical examples of the wireless communication system may include, but are not limited to, a MISO (Multi Input Single Output) system and a SIMO (Single Input Multi Output) system. In the MISO system, the transmitter station has a plurality of antenna elements and the receiver station has a single antenna element. In the SIMO system, the transmitter station has a single antenna element and the receiver station has a plurality of antenna elements.
The number of propagation paths or channels that are spatially established between the transmitter and receiver stations depends on the number of the antenna elements of the transmitter and receiver stations. In order to increase the number of the paths, it is necessary to increase the number of the antenna elements while increasing the scale or dimension of a set of the antenna elements. Increasing the scale or dimension of the set of the antenna elements increases the restriction on mounting the antenna elements on a communication terminal such as a mobile terminal and also increases a manufacturing cost thereof. When the plural antenna elements are provided on a communication terminal having a small size, it may be necessary to reduce a distance between the antenna elements so as to satisfy the restriction condition for mounting the antenna elements. Reducing the distance between the antenna elements increases a correlation between the antenna elements, thereby making it difficult to identify spatial channels that transmit or propagate radio waves and reducing an amount of information that can be actually transmitted. It is desired to ensure that the number of the spatial propagation paths between the transmitter and receiver stations be independent from the number of the antenna elements of the transmitter and receiver stations.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved system, method and/or apparatus. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.